From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id B50F5ECAAD4 for ; Sun, 4 Sep 2022 13:49:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233625AbiIDNto (ORCPT ); Sun, 4 Sep 2022 09:49:44 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60006 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232793AbiIDNti (ORCPT ); Sun, 4 Sep 2022 09:49:38 -0400 Received: from mout.kundenserver.de (mout.kundenserver.de [212.227.126.133]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 260E7EE29; Sun, 4 Sep 2022 06:49:35 -0700 (PDT) Received: from [192.168.1.138] ([37.4.248.23]) by mrelayeu.kundenserver.de (mreue010 [212.227.15.167]) with ESMTPSA (Nemesis) id 1MxV8b-1pJeKH3jY1-00xpCC; Sun, 04 Sep 2022 15:49:13 +0200 Message-ID: <9afe7000-d4c7-0b67-1dfd-7200efe73c0e@i2se.com> Date: Sun, 4 Sep 2022 15:49:11 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.11.0 Subject: Re: [PATCH v4] clk: bcm2835: Round UART input clock up Content-Language: en-US To: "Ivan T. Ivanov" , Michael Turquette , Stephen Boyd , Florian Fainelli , Ray Jui , Scott Branden , Broadcom internal kernel review list , Paul Walmsley , Palmer Dabbelt , Albert Ou , Maxime Ripard , Nicolas Saenz Julienne Cc: Phil Elwell , kernel test robot , linux-clk@vger.kernel.org, linux-rpi-kernel@lists.infradead.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org References: <20220829132943.144608-1-iivanov@suse.de> From: Stefan Wahren In-Reply-To: <20220829132943.144608-1-iivanov@suse.de> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Provags-ID: V03:K1:YOR8PzuYn1YtGuD1bVX7oiT3qrgTf+omYyvhdw/ZqL9xDSoCYBE duBCBWHQLt4IqsOAASUfFThCrPFeNw09587dL2dmbn57MDbW0/a0dZQkLEgkB0huJL6yz+S 1+KAZ/dVlwbSiCZmHL38WVdijHZew1gGX/Qt12rTYnhyX/7JXUNnRCd0LQE6cbHjZ0bc71w Tisgjs0VduAyK3loe7fgg== X-UI-Out-Filterresults: notjunk:1;V03:K0:xopYdvfmTH4=:gvtCwvn2iaYlN2XuPpbNiT 1WogNH/P9FxWmF+trKS87e0Fs+fHvpyJSu5CRzoFK5HI8Ho038VRqq/atYUVh92GGdlP3wkqw 5srDZi+OtEuIWQLm7tO16Jyxs6KzyaSafzaHgKVGGIxG74myCHettadrjhDYPAW6+aW63BwW4 vBGG25FzehgMFU9ugL5hT7wE45ywORC2wDF5EpByixunDaa1NxaWcO+8r0PGIp2X//Wj0dgJP xixsIGyDttQ+Mk+MA9MaPA040tzRI0hxmq5/BYY0EAwfShnnu5KOfvmiHxRHjsWJ6d+L3kgbP NZS3R6ycD4Fan/2uw2doL5gkxW9LJom20LZS7cVoQYLv+nq2cTsttd1veJlZVXNsC57q/NCM4 D4433raH5Oi8qHC4EOSsnKhnaFOdsPdgh4JSZLPLTjOcXnteQ3RJrBh/tmhvlQiQOSQWUig0g pnkTtetBVMEU7JLQdIiDvq/txUknq/xMZsKPHbKxqRUx4j+cmymslK9YUvC4nDx4eTkvnxqcB A5w5ZpUSckrBevKCBQvX2+fqxOqxGZEjZAc7q1fYZneIuczp/Ebk8d74Z/oiDBRhq9vM7aiMI AO9Q+SdwLrmantfZD8V9ma/pmp91fBg6kVhDK1NN2TKJdGlz+nXYCT26I9ypPBInH2oTA4oZY lVH+70kgxCAi9YyYpWx3HcHb+TsS3lIQZuNN4YJs7MqZcA212UyVxr0npttSjbqESBU7zY2da b3mKGSRqCC0fvyqqejz+Urxj9nym7OY+FyqmCVcL3iQgjGKERb80Ap5jFEXFxBX+iQwKaO4of qSylrvI Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Ivan, Am 29.08.22 um 15:29 schrieb Ivan T. Ivanov: > It was reported that RPi3[1] and RPi Zero 2W boards have issues with > the Bluetooth. It turns out that when switching from initial to > operation speed host and device no longer can talk each other because > host uses incorrect UART baud rate. > > The UART driver used in this case is amba-pl011. Original fix, see > below Github link[2], was inside pl011 module, but somehow it didn't > look as the right place to fix. Beside that this original rounding > function is not exactly perfect for all possible clock values. So I > deiced to move the hack to the platform which actually need it. > > The UART clock is initialised to be as close to the requested > frequency as possible without exceeding it. Now that there is a > clock manager that returns the actual frequencies, an expected > 48MHz clock is reported as 47999625. If the requested baud rate > == requested clock/16, there is no headroom and the slight > reduction in actual clock rate results in failure. > > If increasing a clock by less than 0.1% changes it from ..999.. > to ..000.., round it up. > > [1] https://bugzilla.suse.com/show_bug.cgi?id=1188238 > [2] https://github.com/raspberrypi/linux/commit/ab3f1b39537f6d3825b8873006fbe2fc5ff057b7 > > Cc: Phil Elwell > Signed-off-by: Ivan T. Ivanov > --- > > Changes since v3 > * Rework 'scaler' calculation to avoid overflow > * Update Phil Elwell email address > > Changes since v2 > * Added more information in commit message > * Changed hand crafted round function with the one form math.h > > Changes since v1 > Make bcm2835_clock_round() static to fix following warning > when compiling for riscv: > drivers/clk/bcm/clk-bcm2835.c:997:15: warning: no previous prototype for 'bcm2835_clock_round' [-Wmissing-prototypes] > Reported-by: kernel test robot > > drivers/clk/bcm/clk-bcm2835.c | 35 +++++++++++++++++++++++++++++++++-- > 1 file changed, 33 insertions(+), 2 deletions(-) > > diff --git a/drivers/clk/bcm/clk-bcm2835.c b/drivers/clk/bcm/clk-bcm2835.c > index 48a1eb9f2d55..26a5c9a0dd34 100644 > --- a/drivers/clk/bcm/clk-bcm2835.c > +++ b/drivers/clk/bcm/clk-bcm2835.c > @@ -30,6 +30,7 @@ > #include > #include > #include > +#include > #include > #include > #include > @@ -502,6 +503,8 @@ struct bcm2835_clock_data { > bool low_jitter; > > u32 tcnt_mux; > + > + bool round_up; > }; > > struct bcm2835_gate_data { > @@ -993,12 +996,34 @@ static long bcm2835_clock_rate_from_divisor(struct bcm2835_clock *clock, > return temp; > } > > +static unsigned long bcm2835_clock_round(unsigned long clk) sorry, i missed this in my last mail. Please use "rate" instead of "clk" here. > +{ > + unsigned long scaler; > + unsigned long limit;; > + > + limit = clk / 100000; > + > + scaler = 1; > + while (scaler < limit) > + scaler *= 10; > + > + /* > + * If increasing a clock by less than 0.1% changes it > + * from ..999.. to ..000.., round up. > + */ > + if ((clk + scaler - 1) / scaler % 1000 == 0) > + clk = roundup(clk, scaler); > + > + return clk; > +} > + >